MQTT over Websocket?

I'm trying to use wireshark to decode MQTT over Websocket traffic...considering Wireshark already decodes both websocket and MQTT traffic over TCP, this doesn't sound too hard, but I haven't been able to do it.

I've tried many iterations and permutations, but in it's simplest form, I want to get a handle to the existing MQTT dissector from TCP port 1883 (standard port for MQTT over TCP) and install it after the Websocket dissector running on port 8083 (standard port for MQTT over Websocket)...although this LUA does not compile, the idea is something like this...